This invention generally relates to agricultural field spraying equipment, and more particularly to a plot sprayer useful in field research relating to biological effectiveness of agricultural chemicals on crops and weeds.
Agricultural chemicals, including pesticides, plant growth regulators, foliar fertilizers, desiccants and the like, are typically applied to plants or soil by spraying using various types and designs of mobile spraying equipment. The agricultural chemicals are normally diluted, dissolved or dispersed in a suitable liquid carrier, most commonly water, to form a composition that is suitable for spraying and is referred to herein as a xe2x80x9cspray compositionxe2x80x9d. The application rate of a sprayed chemical can be metered by controlling four factors: the rate of travel of the spraying equipment over the ground, the rate at which the spray solution is dispensed, the width of the swath being sprayed, and the concentration of the chemical in the spray solution.
Rate of travel of the spraying equipment, expressed, for example, in meters per second (m/s), is dictated by forward speed during spraying, whether motion is imparted by human power, as in the case of hand-held or backpack-mounted spraying equipment, or by mechanical power, as in the case of tractor-mounted spray equipment or purpose-built motorized spray rigs.
Rate of dispensing, or output, of the spray solution, expressed, for example, in liters per second (l/s), is dictated by several factors: the number of simultaneously operating spray nozzles, the configuration, in particular the size of the orifice of each nozzle, the propulsion force applied (normally provided by hydraulic pressure), and the rheological properties of the spray solution, especially its viscosity. The term xe2x80x9cnozzlexe2x80x9d in the present context is to be understood to apply to any atomization means having the function of a nozzle. Similarly, the term xe2x80x9corificexe2x80x9d in the present context is to be understood to apply to the feature or part of any atomization means having the same function as the orifice of a nozzle.
Spray swath width, expressed, for example, in meters (m), is dictated by the number of nozzles arranged on a boom disposed perpendicularly to the direction of travel of the spray equipment, the distance between nozzles, the angular width of the conical or fan-shaped spray pattern generated by the orifice of each nozzle, the degree of overlap of adjacent spray patterns, and the height of the nozzles above the ground or plant target.
Concentration of the chemical in the spray solution, expressed for example in grams/liter (g/l), is controlled by the operator during preparation of the spray solution, most commonly by mixing a measured amount of a concentrate formulation having a known concentration of the chemical in a measured volume of water.
Chemical application rate is the product of the above parameters and can be expressed as
R=OC/TW
where R is chemical application rate, O is spray solution output, C is concentration of chemical in the spray solution, T is speed of forward travel and W is swath width. When T is expressed in m/s, W in m, O in 1/s and C in g/l, R is given in grams per square meter (g/m2).
Modern spray equipment can generally be fairly precisely calibrated with respect to the above parameters to deliver a desired chemical application rate. Under ideal weather conditions, such calibration leads to an actual application rate which is more or less constant and reproducible and which varies little (typically +/xe2x88x9210% or less) from the desired rate.
However, weather conditions are seldom ideal. In particular, wind, even a light wind, disturbs the spray pattern sufficiently to compromise accuracy and precision of a well calibrated sprayer. When wind speed and direction vary constantly, a condition known as turbulence, this problem is still more acute. Turbulent air movement frequently occurs near ground level even when air movement a few meters above ground is non-turbulent. This turbulence is often further aggravated by motion of the spray equipment.
An additional source of variation in application rate, even when a sprayer is perfectly calibrated, is vertical movement or oscillation of the spray boom or nozzle caused by travel over an irregular ground surface by a wheeled vehicle carrying the spraying equipment. Such vertical movement can be a problem also with hand-held spray equipment even when operated by an experienced technician walking on level ground. As the spray boom or nozzle is raised or lowered, spray swath width and the degree of overlap of adjacent spray patterns vary, resulting in irregularities in deposition of the spray composition.
Yet another problem is disturbance of soil or plants immediately before, during or immediately after spraying by the moving wheels of a vehicle or the walking feet of an operator carrying the spraying equipment. Such disturbance can take the form, for example, of local compaction of the surface layers of soil, leading to variation in the effectiveness of soil-applied chemicals. Disturbance of plants can affect their biological response to an applied chemical as well as result in accidental transfer of an applied chemical to other plants.
A particularly high degree of accuracy, precision and reproducibility is required when the chemical application is for research purposes. Agricultural researchers must be able to precisely evaluate the effects of particular rates of a chemical on crop and/or weed plants occupying a particular area of a field demarcated for such evaluation. Such a demarcated area is referred to herein as a plot. Typically, researchers compare the performance of plants in a sprayed plot to that in a nearby or adjacent unsprayed control plot. Generally, several different chemical treatments are compared, each treatment being applied to a different plot. It is important, therefore, that the chemical is precisely dispensed only on the intended plot, and uniformly within that plot, with little or no wind-assisted drift of the spray solution on to adjacent plots.
The occurrence of wind is, in most climates, very frequent. If spraying has to be restricted to periods of relative calm, the number of plots that can be sprayed in a season is limited. Research productivity suffers as spray operators are often unable to apply chemicals at the optimum time, because of windy weather. Thus, a need exists in the art for a spraying apparatus which is able to accurately dispense a chemical within a plot with minimum effects from wind and turbulence. Such an apparatus would greatly improve research productivity as well as accuracy.
As spraying can seldom wait until conditions are absolutely calm, researchers have to some extent adapted their procedures to allow for at least a light wind. For example, it is common to leave buffer strips between plots to avoid wind-assisted drift from one plot contaminating adjacent plots. The need for buffer strips increases the amount of land needed for field testing of agricultural chemicals, or reduces the number of treatments that can be accommodated in a single experiment. As the experimental area becomes larger, variability in soil and plant conditions increases, tending to reduce the precision of the experiment. A further benefit of a windproof spraying apparatus would therefore be to reduce the amount of land required for a field experiment and thereby to improve the precision of such an experiment.
Previous attempts to provide spraying equipment with wind protection have involved partially or totally surrounding a spray boom, or individual spray nozzles on a boom, with a shield or skirt which is carried on the boom. Shielded sprayers of this type do reduce wind-assisted drift of spray solution, and can also be used to protect plants sensitive to a chemical from spray application of the chemical close to such plants (for example, in selective application of a herbicide to weeds between the rows of a crop). However, a new problem is introduced which is of particular relevance in research plots. The shield or skirt tends to become coated with the chemical and transfers chemical to plants as it passes over them. Further, the spray solution drips from the bottom edge of the shield or skirt. In these and other ways, shielded sprayers of prior art contribute to inaccuracy of application.
There is a long-standing need for improved spraying apparatus that can precisely apply an agricultural chemical treatment to a plot in variable wind conditions, and that minimizes the need for buffer strips between plots. An improved spraying apparatus that meets this need, and at the same time eliminates vertical movement or oscillation of the spray boom or nozzle would be a particularly useful advance in the art. An improved spraying apparatus that has these benefits, and that in operation causes no disturbance of soil or plants other than the direct effects of spraying, would be an even more useful advance in the art. It is just such an improved spraying apparatus that is now provided.
The present invention relates to a spray apparatus for spraying a plot of land with a liquid spray composition. The spray apparatus is readily relocatable without disassembly and comprises (1) a rigid frame; (2) a wind shield, supported on or integral with the frame, comprising a side wall that defines an enclosed area and has a top edge that is preferably substantially horizontal and is located at a suitable height; (3) a track assembly located within the enclosed area and supported on the frame; (4) a spray assembly mounted on the track assembly and movable thereon in at least one horizontal direction relative to the wind shield, the spray assembly comprising atomizing means located at a height lower than any substantial part of the top edge of the side wall; (5) a permanent or replaceable reservoir external to or integral with the spray assembly, adapted to hold a liquid spray composition and operatively connected to the atomizing means to supply the spray composition thereto; (6) means for transmission of power to the spray assembly for movement thereof on the track assembly; (7) drive control means, to permit operator control of said movement of the spray assembly; (8) fluid propulsion means, i.e., means for causing the spray composition to flow from the reservoir through the atomizing means, to effect spraying; (9) flow control means, to permit operator control of spraying; and (10) means for moving the apparatus vertically and horizontally, such that the apparatus is readily relocatable without disassembly.
By xe2x80x9creadily relocatablexe2x80x9d it is meant that the entire apparatus can be transported laterally from one plot to another in a field by a small number of persons acting together, or with the aid of conventional farm machinery. The frame is of such construction, and the other components of the apparatus are disposed with respect to the frame in such a manner, as to permit easy relocation of the entire apparatus without disassembly. Means for moving the apparatus vertically and horizontally can take a number of forms. For example, the frame can be provided with optionally retractable wheels, to enable the apparatus to be moved laterally from one plot to another. Preferably, however, the frame is provided with lifting means, to facilitate raising of the entire apparatus off the ground at the location of a first plot, transporting of the apparatus to the location of a second plot, and lowering of the apparatus on to the ground at the location of the second plot. Such lifting means can be, for example, a plurality of handles to permit raising, transporting and lowering by two or more persons. In preferred embodiments, the lifting means are hitching means, by which the apparatus can be hitched to a tractor or other powered vehicle capable of raising, transporting and lowering the apparatus. Such hitching means typically comprise a plurality of hitching points and can be adapted, for example, for connection to a conventional tractor-mounted three-point hitch or fork-lift device.
The side wall of the wind shield preferably comprises four substantially rectangular side panels that are substantially vertical and are connected to each other at approximately 90xc2x0 angles. The side panels can be of substantially equal length so as to define a square enclosed area; however for most applications it is preferred that there be a longer pair and a shorter pair of opposing side panels, thereby defining a substantially rectangular enclosed area. The wind shield preferably further comprises a substantially horizontal, square or rectangular top canopy which is connected to the side wall, for example at or close to the top edge thereof, so as to leave substantially no gaps between the top canopy and the side panels.
In one embodiment the side panels, and optionally the top canopy, are of rigid construction and have sufficient mechanical strength and rigidity to serve both as the wind shield and as the frame. In this embodiment, therefore, the wind shield is integral with the frame. However, for most purposes it is preferred that the wind shield and frame are not integral, and that the side panels and top canopy are constructed of a lightweight material attached directly to the frame. It is especially preferred that this material be transparent, to permit operation of the spray assembly within the enclosed area to be visually monitored by a person standing outside the wind shield.
It is also preferred that at least one of the side panels or the top canopy be provided with an aperture large enough to permit insertion, removal or servicing of a reservoir. This aperture facilitates replacement or refilling of the reservoir after a plot has been sprayed and the spray apparatus has been, or is about to be, moved to another plot.
The track assembly, in one embodiment of the invention, comprises a single fixed horizontal track, typically oriented parallel to the longer pair of side panels and midway between them. On such a track the spray assembly is movable in one direction only. In another embodiment of the invention, the track assembly comprises a first track mounted fixedly on the rigid frame and a second track mounted movably on the first track, both of these tracks being located within the enclosed area. The first and second tracks are oriented perpendicularly to each other, the first track being typically oriented parallel to the longer pair of side panels and midway between them. In this embodiment, the spray assembly is movably mounted on the second track. The first and second tracks are movably connected by a carriage. This arrangement allows the spray assembly to be moved across a plot in any desired pattern, for example in a scan pattern that includes a series of parallel passes.
The spray assembly comprises atomizing means which is preferably a hydraulic nozzle or a plurality of such nozzles. In an embodiment of the invention having a single fixed track on which the spray assembly is mounted, a preferred spray assembly comprises a boom oriented perpendicularly to the track, with a plurality of nozzles mounted at substantially regular intervals along the boom. The boom supports the nozzles and forms or carries a portion of a conduit through which a liquid spray composition can flow from the reservoir to all of the nozzles.
In a particularly preferred embodiment having only one nozzle, the spray assembly is movable horizontally in a first direction and a second direction perpendicular to the first direction so as to be capable of uniformly spraying the entire enclosed area. This is preferably accomplished using a track assembly comprising two perpendicular tracks as described above, wherein the second track is mounted movably on the first track and the spray assembly is mounted movably on the second track. Most preferably in this embodiment, the reservoir is integral with the spray assembly, i.e., is part of the spray assembly itself rather than being located elsewhere in the apparatus, and is connected to the nozzle by a rigid coupling piece having an internal conduit through which the spray composition is fed from the reservoir to the nozzle. This coupling piece can incorporate a quick-release coupling to permit easy replacement of the reservoir with minimal spillage of unused spray composition.
Drive means to cause the spray assembly to move on the track assembly (including, in an embodiment with two perpendicular tracks, drive means to cause the carriage carrying the second track to move on the first track) can be internal to the spray apparatus but is preferably external, the spray apparatus itself having an operative connection to such external drive means. For example, the external drive means can comprise an electric power generator and the operative connection can comprise a power cable that leads to an electric motor forming part of the track assembly and providing motive force to propel the spray assembly. As another example, the external drive means can comprise a source of hydraulic power and the operative connection can comprise a system of pipes providing hydraulic pressure to propel the spray assembly. In the embodiment described above wherein the track assembly comprises perpendicular first and second tracks movably connected by a carriage, an operative connection to drive means is provided both to the carriage, permitting movement of the second track on the first track, and to the spray assembly, permitting its movement on the second track.
Drive control means can comprise electrical switches and/or hydraulic valves, operatively connected to a control panel. The drive control means can be automated to varying degrees; in a preferred embodiment all aspects of motion and operation of the spray assembly, including spraying, are programmably controlled by a computer.
Fluid propulsion means, to cause the liquid spray composition to flow from the reservoir through the atomizing means, can be internal to the spray apparatus or external thereto. Flow can occur by gravity feed, for example to a spinning disk atomizer which draws the spray composition through at a constant rate, controllable by the speed of rotation of the spinning disk. Electrical power to drive a spinning disk can be provided from an external source (e.g., a generator) or a source located within the apparatus (e.g. a battery pack). Preferably, however, the fluid propulsion means is hydraulic pressure provided by pressurized gas, in which case the preferred atomizing means is a hydraulic nozzle or plurality of such nozzles. Pressurized gas, for example carbon dioxide, nitrogen, air or propane, can be supplied from a bottle. Alternatively, it can be supplied directly from a compressor. In either case the pressurized gas is supplied to the reservoir by an airline running from the source of pressurized gas to the reservoir. The term xe2x80x9cairlinexe2x80x9d as used herein means a conduit for pressurized gas not restricted to compressed air.
Flow control means typically comprises one or more valves in the airline and/or in a conduit through which the spray composition flows from the reservoir to the atomizing means. Such valves can be designed for manual operation or can be computer controlled. In the embodiment described above wherein the track assembly comprises perpendicular first and second tracks movably connected by a carriage, the flow control means can be configured to cause spraying to occur when the spray assembly is in motion in a first direction parallel to the first track, and to prevent spraying when the spray assembly is stationary or in motion in a second direction parallel to the second track.
The present invention also relates to a process for spraying a plot using a spray apparatus as described herein. This process comprises the steps of (1) positioning the apparatus in a field such that the enclosed area defined by the wind shield covers the plot; (2) adding a suitable quantity of a spray composition to a permanent reservoir, or coupling a replaceable reservoir containing a spray composition to a spray assembly adapted to receive such a replaceable reservoir; and thereafter (3) operating, or causing a computer control system to operate, a switch or plurality of switches to cause the spray assembly to move in a predetermined pattern across the plot and to spray the spray composition uniformly over the entire plot. Steps (1) and (2) of this process can be carried out in either order.
The spray apparatus of the invention is particularly adapted for consecutively spraying a plurality of plots, for example in implementation of an agricultural chemical field trial. Accordingly, a process is provided for consecutively spraying a plurality of plots using a spray apparatus as described herein, comprising carrying out steps (1), (2) and (3) as described above; followed by (4) releasing unused spray composition from a permanent reservoir and rinsing the reservoir, or uncoupling a replaceable reservoir from the spray assembly; and (5) repeating steps (1) to (4) with further spray compositions on second and subsequent plots until all plots have been sprayed.
The present invention overcomes the problems of prior art sprayers by providing an easily relocatable, lightweight enclosure which is stationary during operation and a spray assembly for spraying a liquid spray composition within the area defined by the enclosure, which can correspond to the area of a plot. The apparatus of the present invention provides more accurate application of spray compositions to plots, and more uniform application across a single plot than prior spray equipment. The improved accuracy and uniformity can result from elimination of wind and turbulence, or from absence of vertical movement or oscillation of the spray assembly, or both. The apparatus also eliminates disturbance of soil or plants within plots by wheel-tracking or trampling. The present invention in one embodiment also permits rapid application of numerous spray compositions consecutively to different plots, without the risk of contamination of one spray composition by remnants of a previously applied spray composition in the apparatus. Because of these and other advantages, agricultural researchers can apply spray compositions to test plots more rapidly and accurately than in the past, and this can improve the speed, accuracy and productivity of their research.